In humans and many other animals, cartilage is present on the surface of bones that form articular joints to facilitate articulation of the joint and protect and cushion the bones. However, defects may develop in the cartilage from various causes such as abrupt trauma or prolonged wear. A number of techniques have been attempted to treat such cartilage defects. One such technique is the transplantation of fresh osteochondral allografts.
In this procedure, an allograft plug, also known as a osteochondral plug or core, is harvested from a condyle or rounded joint-forming portion of a donor bone. Intact on the surface of the allograft plug, on a portion of the bone known as the cartilage plate, is healthy cartilage. The allograft plug may also have attached to the cartilage plate cancellous tissue, which is the porous inner material that is present in many bones. In the recipient patient, the cartilage defect and the corresponding portion of underlying bone are cutaway and removed from the joint. The allograft plug is then inserted and attached to the cutaway portion so that the cartilage plate and healthy cartilage of the allograft plug align with the cartilage on the surface of the host bone.
One problem that arises with osteochondral allografts is that the recipient may adversely respond or reject the allograft plug. This can happen primarily because of the antigenic material contained in the cancellous bone of the allograft plug. Occurrence of such an adverse response may result in the recipient site reforming or healing in such a manner that the allograft plug becomes walled off from the host bone thereby delaying or preventing incorporation of the allograft. In addition, physically attaching and securing the allograft plug to the recipient site presents difficulties.